The present invention relates to an information recording medium, reproduction method, and discrimination method and, more particularly, to an information recording medium subjected to a forgery and/or fraudulent use preventive measure, a method of reproducing information recorded on the information recording medium, and a method of discriminating an information recording medium whose genuineness is unknown between a genuine article and a counterfeit.
Recently, the performance of input/output apparatuses such as scanners, printers, and copying machines, personal computers, and image processing software has advanced, so even a commercially available apparatus is capable of high-accuracy forgery. To meet the situation, securities and ID cards for personal identification use various forgery preventive techniques.
One forgery preventive technique is to record security information as a latent image (invisible information). A magnetic forgery preventive technique is a representative forgery preventive technique using a latent image. For example, a printed portion using magnetic ink containing a magnetic powder is formed in a predetermined position of a security, and the genuineness thereof is checked by detecting the presence/absence of magnetism or a magnetic pattern. Also, information is magnetically recorded on a magnetic stripe of an ID card, and identification of an individual is performed by reproducing the information.
Unfortunately, the magnetic forgery preventive technique requires a dedicated, expensive reproducing apparatus for reproducing information recorded as a latent image. Also, a person having a little expert knowledge can readily read recorded information. Therefore, this magnetic forgery preventive technique has low immunity to forgery, so a highly secure technique is being demanded.
In addition to the forgery preventive techniques using a latent image, forgery preventive techniques using a hologram or a diffraction pattern are also known. For example, hologram patterns are formed on many ID cards, and hologram slits are formed on paper money and merchandise coupons in certain countries.
The recent progress of the hologram technique makes it possible to obtain highly visible fine diffraction images. However, the manufacture thereof requires advanced techniques, and this increases the manufacturing cost. In addition, a hologram is generally difficult to copy and is therefore considered to be effective as a forgery preventing means, but a light diffraction structure like this can be obtained by duplication technique. Hence, the same light diffraction structure is used for the same type of ID cards. Accordingly, it is readily possible to cut out a hologram portion from a genuine credit card and paste the hologram on a forged credit card.